Phenoxy herbicides, especially 2,4-D, is well known in the art as an effective herbicide for the control broad leaf weeds. From this point on, we will use 2,4-D as the example but those skilled in the an should realize that although 2,4-D is mentioned it should be understood that it also applies generally to the entire phenoxy herbicide family.
It is a common practice for farmers to add 2,4-D amine herbicide to a concentrated liquid fertilizer (such a 28% N) and to spray it without further dilution with water. 2,4-D amine herbicide is also widely used together with other herbicides and diluted fertilizers such as ammonium sulfate (AMS) to enhance the bioefficacy and to achieve a broader weed control spectrum. However, 2,4-D acid and its non-amine salts have very low solubility in water. Because of this, the most commonly used 2,4-D herbicide is 2,4-D amine salts. Although hydrophobic 2,4-D esters are available, 2,4-D formulated and applied as a water-soluble salt has the added advantages of not requiring an emulsifier and/or an organic solvent.
It is a common practice for farmers to mix various products in a spray tank for convenience and economy reasons. For example, farmers may mix together a 2,4-D product and a fertilizer product. However, when a 2,4-D amine product is mixed with another product that contains non-amine cations, such as ammonium, sodium, potassium, and multivalent ions, a precipitate can form in the spray tank resulting in the blockage of the spray nozzle. Even if farmers intentionally try to avoid mixing 2,4-D with incompatible components, it may not be possible to avoid having both 2,4-D anion and non-amine cations in the same spray tank because ammonium, K, Na, Ca, and Mg may come from, for example, fertilizers, other herbicide formulations, micronutrients, or hard water, thereby causing unwanted precipitate. Farmers have been trying to solve this precipitate problem by adding traditional compatibility agents or hydrotropes such as phosphate esters, glycols, or alcohol without satisfactory result.
Accordingly, it is desirable to develop a method for minimizing the formation of nozzle plugging precipitate in a vessel containing a 2,4-D herbicide and non-amine cations.
It is, therefore, an objective of the present invention to provide a method for minimizing the formation of nozzle plugging precipitate in a vessel containing a 2,4-D herbicide and non-amine cations by using a suitable compatibility agent. It is a further and preferred objective to provide a method of using a surfactant which not only functions as a compatibility agent for precipitation crystal-free spray application but also as an adjuvant for improved efficacy.